An electrophotographic image forming apparatus, such as a printer, a copier, a facsimile machine or a multifunctional peripheral (MFP), includes a photosensitive medium, an exposing device to emit a laser beam onto the photosensitive medium to thereby form an electrostatic latent image corresponding to image data on the photosensitive medium, and a developing device to supply toner to the photosensitive medium to develop the electrostatic latent image formed on photosensitive medium.
The developing device includes a developing case to house toner, a developing roller, a toner supply roller, an agitator to agitate toner, a toner receptacle, a toner transfer unit and a waste toner chamber.
The developing device may also includes various sealing members to prevent toner from leaking out from rotating parts of each roller, and from portions in frictional contact with the rotating parts. These sealing members require high elastic resilience in order to maintain air-tight seals. To that end, a double-sided tape is typically attached to a sponge to fix the sponge to portions of the developing device.
For example, referring to FIG. 1C, a conventional sponge sealing member 100 is disposed in a housing 200 of an image forming apparatus, to prevent toner leakage and image contamination. The sponge sealing member 100 may be disposed in a portion of the housing 200 where three or more surfaces meet.
FIG. 1D shows a sectional view of the sponge sealing member 100. The double-sided tape 110 is attached to the bottom of the sponge sealing member 100, between an upper sponge 130 and a lower sponge 140, and between a felt portion 120 and the upper sponge 130, so that the felt portion 120, the upper sponge 130 and the lower sponge 140 are attached to each other.
However, when the housing 200 functions as a developing device and is used with the sponge sealing member 100, de-lamination may occurs in the sponge sealing member 100, which may reduce the adhesiveness of the sponge sealing member 100, which in turn, after a period of usage, result in toner scattering or leaking out during driving of the housing 200, causing image contamination.
FIG. 1A illustrates an example where two surfaces of the conventional sponge sealing member 100 are in contact with two surfaces of the housing 200. In this situation, a space is formed at the corner between the sponge sealing member 100 and the housing 200. Accordingly, toner or developer may leak out through the space from the housing 200.
FIG. 1B illustrates a conventional sponge sealing member 100 divided into two portions. Each of the two portions is attached to a respective surface of the housing 200, so it may be possible to prevent the formation of the space shown in FIG. 1A, but the manufacturing process is complicated and it is difficult to correctly attach each of the two portions of the sponge sealing member 100 to a corner between the two surfaces of the housing 200.
The problem may become more prominent when a portion of an image forming apparatus with a complicated structure, such as a corner in which three or more surfaces meet, requires sealing.
For example, it may be difficult to place the conventional sponge sealing member 100 in a portion with such complicated structure. When the sponge sealing member 100 is attached to a corner of the housing 200 in which two or more surfaces meet, the sponge sealing member 100 needs to be broken into pieces of correct sizes and/or shapes to fit into the corner. However, since the sponge sealing member 100 bends due to its elasticity, it is practically difficult to properly size the sections of the sponge sealing member 100 to sufficiently seal the corner.
For example, each of the plurality of sponge sealing members may have a thickness of about 2 mm to about 5 mm, and has a low hardness due to its elastic nature. Typically, during attachment to the housing, the sponge sealing members is held with tweezers. The use of the tweezers causes a change in the shape of the sponge sealing members, making it difficult to correctly size the sponge sealing members to fit into the corner. A space may thus be formed between the sponge sealing member 100 and the housing 200.
Conventionally, a plurality of sponge sealing members may be overlappingly attached to a housing, in order to seal a portion of the housing, for example at a corner, at which three or more surfaces. However, various problems may occur when multiple sponge sealing members are used in such a manner.
For example, when a plurality of sponge sealing members are attached to the housing, manufacturing costs may increase due to the increase in the number of sealing members. It may also be difficult to completely seal a corner between the housing and the plurality of sponge sealing members as discussed above.
Additionally, since porous sponges are used as sealing members, toner may be absorbed into the porous sponges, and may eventually leak out.
If contamination occurs inside the image forming apparatus, image contamination will continue to occur even when a new developing device housing is installed to replace the old one with its supply of toner exhausted.
FIGS. 4 and 5 illustrate a usage of sealing member in an image forming apparatus.
A sealing member 214 shown in FIG. 4 in the form of a liquid adhesive is poured onto a surface to be sealed. After a predetermined period of time has elapsed, the sealing member 214 is converted into solid, and the sealing operation is finished. A sealing member 215 shown in FIG. 5 performs the sealing operation in the same manner as that of FIG. 4. However, such sealing members 214 and 215 are sticky due to their high viscosity. It is thus difficult to properly place the sealing members 214 and 215 at a corner of a housing 200 to be sealed with the sealing members 214 and 215. A space may be formed at the corner, through which toner may leak out from the housing 200, similarly with the situation in which sealing is performed using the sponge sealing member 100 as described above.
To prevent toner leakage caused by the formation of spaces or gaps between the housing and the sealing member, there is a need to pour a large amount of a sealing material, e.g., in the form of a liquid adhesive, but it is difficult to expect a sufficient sealing effect. Therefore, a conventional sealing member in the form of a liquid adhesive is typically used to prevent toner from leaking through pores on a plane rather than for prevention of leakage through a corner having a complicated shape.